1. Field of the Invention
The present invention relates to a chemical-amplification-type negative resist composition which can be suitably used in the field of manufacturing electronic parts such as semiconductor devices and liquid-crystal display devices, can be developed under an alkaline condition, is capable of achieving a resist pattern exhibiting excellent definition and profile, exhibits consistent performance which is less dependent on the type of substrate the negative resist composition and achieves a minimized change in the sensitivety and film thickness with the passage of time and a satisfactory PEG margin.
2. Description of the Related Art
Resists used in the field of manufacturing electronic parts such as semiconductor devices and liquid-crystal display devices may be a positive type or a negative type. With the former, when the resist is developed, the portion irradiated with active rays is removed, thus forming a positive pattern. With the latter, the non-irradiated portion is removed, thus forming a negative pattern. As one such negative resist, a chemical-amplification-type negative resist has been known which principally consists of an alkali-soluble resin, a compound capable of generating an acid by irradiation, and a crosslinking agent.
For example, Japanese Patent Laid-Open No. 62-164045 discloses a negative photoresist principally consisting of an acid-setting resin system and a photo-acid-generating agent contained at in amount sufficient to form a thermostable negative image and selected from the group of halogenated organic compounds, and characterized in that the halogenated organic compound selectively absorbs chemical rays within the range from 210 to 299 nm, has miscibility with the acid-setting resin, can be developed in an alkaline solution, and is capable of generating a halide acid when irradiated with far-ultraviolet rays for crosslinking the acid-setting resin, under an increasing temperature.
Further, Japanese Patent Laid-Open No. 7-146556 discloses a negative photosensitive composition principally consisting of an alkali-soluble resin, a photo-acid-generating agent system, and a crosslinking agent which acts on the alkali-soluble resin under acidic conditions, and characterized in that the crosslinking agent is a higher-alkyl-type alkoxymethylmelamine resin, and the monomer content of the alkoxymethylmelamine resin is 5 to 40% by weight.
In these chemical-amplification-type negative photoresist compositions, an image is formed by the catalytic activity of the acid generated by irradiation, the sensitivity is high, and a resist pattern exhibiting high resolution can be obtained by alkali development. Because of such advantages, they are suitably used in the field of manufacturing electronic parts where finer processing is increasingly required, and particularly, for manufacturing semiconductor devices and liquid-crystal display devices.
Such resists of the related arts, however, can no any longer sufficiently satisfy the resolution level recently required in the field of manufacturing electronic parts, and cannot achieve a pattern exhibiting an excellent profile. In addition to these problems, such resists are dependent on the substrate, and such a dependency causes a problem in the practical use of the resist since the resist properties vary in relation to the type of substrate used.
An object of the present invention is to provide a chemical-amplification-type negative resist which exhibits further improved resolution and an excellent profile, and which has a reduced dependency on the type of substrate.
Furthermore, a chemical-amplification-type photoresist containing a carboxylic acid and an amine is proposed in EP749046A1, but this is a positive photoresist.
As described in the claims of the aforementioned EP publication, such a positive photoresist principally consists of a photo-acid-generating agent capable of generating an acid by irradiation, and a resin ingredient, which solubility in an alkaline aqueous solution is enhanced by the activity of an acid. The resin ingredient includes a polyhydroxystyrene having hydroxy groups each protected by a group (hereinafter simply referred to as protective group) capable of suppressing solubility to an alkali and dissociating by the activity of the acid.
According to this principle composition, the protective groups of the initially alkali-insoluble resin ingredient in the portion irradiated with active rays are dissociating according to the activity of the acid generated by irradiation and the resin ingredient changes to alkali-soluble, and to the contrary, the non-irradiated portion remains insoluble in an alkali. Thus the irradiated portion is removed when developed to form a positive pattern.
On the contrary, as aforementioned, a chemical-amplification-type negative resist principally consists of a photo-acid-generating agent, an alkali-soluble resin, and a crosslinking agent, and in the irradiated portion the alkali-soluble resin and the crosslinking agent are crosslinked according to the activity of the acid generated by irradiation, thus the irradiated portion changes from alkali-soluble to alkali-insoluble, whereas the non-irradiated portion remains alkali-soluble, which phenomena is opposite to that in a positive photoresist. Thus, the non-irradiated portion is removed to form a negative pattern.
As the crosslinking agent, melamine resins, urea resins and other amino resins each having a hydroxymethyl group or an alkoxymethyl group in the N-position are employed. Whereas these resins are excellent in crosslinking properties in the presence of an acid, they are unstable in a resist composition solution and their sensitivity and thickness of the resultant resist film obtained by application (hereinafter simply referred to as "film thickness") are liable to change with the passage of time.
In the manufacturing of semiconductor devices, manufacturing lines are operated for mass production each in accordance with a predetermined sensitivity and film thickness, deviations in sensitivity and/or film thickness deteriorate productivity of semiconductor devices.
Further, dissociation of protective groups or crosslinking according to the activity of an acid of a positive or negative chemical-amplification-type resist respectively occurs during post exposure baking treatment (hereinafter briefly referred to as "PEB"), so that the PEB largely affects the resolution and the shape of resist pattern.
In particular, since the negative photoresist has a large dependency of crosslinking reaction on the temperature of PEB, a deviation from a given temperature of PEB increases the difference in dimensions between a mask pattern and a resultant resist pattern.
Accordingly, demands have been made to provide a negative photoresist having a reduced PEB-dependency, that is, an excellent PEB margin which can provide a desired size of resist pattern within as wide a range of PEB temperature as possible.
Therefore, another object of the invention is to provide a chemical-amplification-type negative resist which has a minimized change in the sensitivity and film thickness and has a satisfactory PEB margin.